[Maxima-bugs] [ maxima-Bugs-3152753 ] function definition doesn't update

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Bugs item #3152753, was opened at 2011-01-06 22:30
Message generated for change (Comment added) made by willisbl
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Category: Lisp Core
Group: None
Status: Open
Resolution: None
Priority: 9
Private: No
Submitted By: Van (lvwarren)
Assigned to: Nobody/Anonymous (nobody)
Summary: function definition doesn't update

Initial Comment:
In two consecutive cells enter:
h[i,j]:= i+j;
then
genmatrix(h,2,2);

Evaluate both cells. Then make any change to h[i,j] and reevaluate. The new definition is not used. See attached.

Maxima version: 5.22.1
Maxima build date: 11:48 8/13/2010
Host type: i686-pc-mingw32
Lisp implementation type: GNU Common Lisp (GCL)
Lisp implementation version: GCL 2.6.8

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>Comment By: Barton Willis (willisbl)
Date: 2011-01-07 07:19

Message:
This isn't a bug. The statement  h[i,j]:= i+j defines a memoizing function.
 To redefine a memoizing function, first use remarray; example:

(%i1) a[i] := 5;
(%o1) a[i]:=5
(%i2) a[7];
(%o2) 5
(%i3) a[i] := 8;
(%o3) a[i]:=8
(%i4) a[7];
(%o4) 5
(%i5) a[42];
(%o5) 8
(%i6) remarray(a);
(%o6) [a]
(%i7) a[i] := 8;
(%o7) a[i]:=8
(%i8) a[7];
(%o8) 8

I'd guess that the user documentation isn't all that clear about this.



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